It is often necessary to remove unwanted particles and gasses from fluids by filtering. An example of this is in the infusion of physiological fluids, including blood and blood products. The removal of gasses is even more important when the fluids have been warmed, because of the outgassing caused by the warming.
Because the particles, gasses, and fluid have different densities, it is known to separate these by centrifugal forces arising in a vortex generated in the fluid. Thus, it is known to provide the fluids to a separation chamber by way of an inlet that is tangential to the chamber. The entering fluids are directed into a circular flow pattern, and the gasses tend to accumulate in the center of the chamber while the heavier particles and fluids go to the outside of the chamber. The gasses are allowed to exit the chamber through a vent, and the particles are removed from the fluid by a physical filter.
These devices have faced several problems, particularly when used with cellular fluids. One problem has been the formation of a vortex large enough to remove substantial amounts of gas. The physical arrangement of the various elements of prior devices has constricted the vortex, preventing effective removal of gas. Further, prior art devices have not generally allowed the operator to view operation of the vortex, thus precluding easy verification of proper operation of the device.
Another problem has been clogging due to build up of particulates and cellular globules in the filter medium. This buildup can effectively block the passage of gasses and prevent their separation from the fluid.
A further feature employed in this type of device is that of a check valve. A check valve is placed in the outlet line for stopping further flow through the device when it becomes full of removed air. This occurs, for example, when the amount of air in the fluid exceeds the ability of the device to remove it. Because of the danger of infusing air, or other gasses, into the patient, a check valve that senses the presence of excess air must be placed in the outlet line to block flow of the gasses to the patient. In some instances, these check valves are separate from the filter, which complicates manufacture, inventory, and assembly. Further, prior art check valves often become stuck in the closed position or inhibit fluid flow when open by entrainment of the valve in the fluid flow.
It is an object of this invention to overcome these and other defects by a filter that is compact, easily manufactured, and efficient.